Phospholipids are important components of cell membranes of plants, microbes and animals. The term “phospholipid”, refers to compounds derived from fatty acids and a phosphate-containing compound attached to glycerol or the amino alcohol sphingosine, resulting in compounds with fat-soluble and water-soluble regions. The term “lecithin” herein is used for mixtures of phospholipids and triglycerides. The main glycerol-containing phospholipids in lecithin are phosphatidyl choline, phosphatidyl inositol, phosphatidyl ethanolamine and phosphatidic acid, further referred to herein as PC, PI, PE, and PA, respectively. The actual composition of phospholipids depends on the source. A further term employed for highly polar components of lecithin are acetone insolubles, further referred to as AI herein. These are lecithin components that are generally insoluble in phospholipid-saturated acetone, which is typically employed to remove neutral triglycerides from crude lecithin.
A number of processes have been developed to fractionate commercially available lecithin, in particular to obtain fractions enriched in phosphatidyl choline.
U.S. Pat. No. 4,235,793 discloses a process for obtaining oily, highly purified phosphatidylcholines from oily raw phosphatides comprising extracting an oily phosphatide extract from the oily raw phosphatide with a solvent selected from the group consisting of lower alcohols and aqueous solutions thereof containing from about 85 to 96 percent alcohol, directly contacting the said oily phosphatide extract with an aluminium oxide adsorbent and recovering the adsorbed phosphatidylcholine therefrom. The process is cumbersome since it requires the use of large amounts of aluminium oxide, and since the treated material also needs to be filtrated to remove adsorbent fines.
WO-A-2005/072477 discloses a method for the separation of phospholipids from a phospholipid containing material, comprising a) combining the phospholipid-containing material and a water soluble aliphatic alcohol, to form a phospholipid-containing fraction; and b) cooling the phospholipid-containing fraction to precipitate the phospholipids. The thus obtained mixture forms two separate fractions, which were separated by gravity, e.g. through centrifugation. The material is then mixed under heating, specifically with isopropanol, n-propanol and mixtures thereof, followed by a cooling step, and the obtained fractions are separated by several centrifugation steps. As a one-stage extraction process, the maximum extract yield of phospholipids is relatively low. Yet further, the process it is not very suitable for a continuous use, and cumbersome due to several centrifugation and reheating and/or cooling steps required.
Accordingly, there remains a need for a process with improved efficiency of phospholipid fractionation, which is also suitable for use on an industrial scale, and in a continuous process.